Heater type vacuum tube



Oct. 20, 1931. J DELANEY 1,828,524

HEATER TYPE VACUUM TUBE Filed March '7, 1928 sz er/ INVENTOR 014M494ffiEZ/M/EY ATTORNEY Patented Oct. 20, 1931 UNITED STATES P.a'rrshrrOFFICE- DANIEL J'. DELANEY, OF EAST NEWARK, NEW JERSEY, ASSIGNOR TOARCTURIJ'S RADIO TUBE COMPANY, OF NEWARK, NEW JERSEY, A

CORPORATION OF DELAWARE HEATER 'TYPE vacuum TUBE Application filed March7,

This invention relates to a vacuum tube of the heater type andparticularly to a cathode Construction for such a tube.

In the co-pending application of Clarence A. Horn, Serial No. 249,256entitled Multiple filament rectifier; filed January 25, 1928, there isshown a full wave rectifying tube of the heater type in which twofilaments I are connected in parallel and are surrounded bycylindricalcathodes which are coated with electron-emitting oxides and in turn aresurrounded by two cylindrical plates or anodes, In this type of vacuumtube the cathode is heated from a filament of carbon or other materialadapted to be raised toincandescence by the current flowingtherethrough, and inasmuch as the heat radiated bythe filamen't variesas the square of, the distance, the cathodes should be placed as closeas possible to the heater in order to utilize a maximum of the heatenergyproduced therein. The electron emission from the outer surface ofthe cathode depends not only on thematerial comprisingthe surface andthe temper.- ature to which itisraised, but also on the amount ofsurface which is energized. To increase the surface willincrease theelectron emission, but where a cylindrical cathode is used such increaseof surface must necessarily increase the diameter of the cathode andtherefore space the walls thereof farther from the heating filament withthe result that the heat energy intercepted by the cathode is materiallyreduced.

It is one of the objects, therefore, of the present invention to-providea cathode in which the electron-emitting surface is considerablyincreased while at the same time the effective distance of the walls ofthecathode from the heater are such that the maximum possible heatenergy th refrom is uti-. lized. r j a Another object ofthe inventionisto provide a cathode for a heater type vacuum tube in which theelectron-emitting surface 18 large enough so that a relatively high termperature for eificientoperation of the tube need not be maintained.

7 Another object of the invention is to pro vide a cathode having greatrigidity so that it 1928. Serial No. 259,647.

especially relating to construction and design thereof will be proceeds.

One embodiment of the invention has been illustrated in the accompanyingdrawings, in which Fig. l is a sectional sideelevation of a vac uum tubeembodying the invention;

' Fig. 2 is a sectional plan view taken on the line 2-2 of Fig. 1 andapparent as the description Fig. 3 is an enlarged perspective View of athe'cathode. I I r Referring more specifically to the drawings, theinvention is shown in "connection with a full wave rectifier tube suchasis illustrated and described in theco-pen'ding application abovereferred to and which comprises an envelope 10 mounted on the usual base11 which carries the pins 12 adapted for making the connections to thesocket terminals when the tube is inserted in the socket. A pair ofplates 13 and 14 are mounted upon uprights 15 and '16, respectively,which are sealed into the usual press (not shown), the upper endsthereof being supported by means of auxiliary posts 15 and 16 which aresealed in the glass bead 17 so as'to insulatingl space y.

upper'ends of the-plates. The plates 13 and 14may be'formed of sheets ofmetal bent in cylindrical form and provided with flanges 18 an'd19 bywhich they may be attached to the PP I'ts15 and 16. A central conductor20 mounted in the center of the tube and fo the support for the cathodes21 and 22 which are mounted inside of the plates 13 and 14. To this enda'strip'23 is welded around the. lowerend of the cathode 21 and a strip24 is welded aroundthe lower end of the cathode 22,'both said strips 23and 24 being welded to the support 20. The support 20 is bent out-'wardlv at a point slightly above its juncture With the strips 23 and 24and then upwardly to a point near the top of the tube and strips 25 and26 which are welded to the upper end ofthe support 20 are secured to theupper ends of the cathodes 21 and 22 in a similar manner.

as the strips 23 and 24 and rigidly support the tops thereof. Filaments27 and 28 are positioned inside of the cathodes 21 and 22 and aresupported at their upper ends by springs 29 and 30 which are attached tothe upper ends of the filaments and welded to the upper end of thecentral supporting post 20. The lower ends of the filaments 27 and 28are attached to supporting rods 31 and 32 which are connected to one ofthe filament terminals of the tube, the central post 20 being connectedto the other filament terminal and forming the conductor for the otherends of the filaments and for the cathodes. The glass head 17 may besealed around and supported by the upper end of the post 20. T

As'outlined above, the construction of the full wave rectifier tube issimilar to that'described and shown iirthe above entitled cope'ndinglapplications The cathode forming the subject matter of the presentinvention comprises a tubular shell 33 having corrugated walls, which,as illustrated in Fig. 3 in the embodiment shown, has five outwardlyextending ridges 34: and five indentations 35 running the full' lengthof the cathode. The strip of supporting material'25 may be circularlybent around thecatho'de and welded to the upper ends of the ridges 341atthe points of contact as shown at 34; two or three such Welds beingsufficient in most cases. The cathode,I of course, is properly coatedwith electron emitting oxides asis well known in the art.

With this construct on it will be evident that the external surface orelectron-emitting surface of the cathode is greatly increased, suchincrease being in one instance, using a similar cathode, about 7 5' percent. The filament may be spaced approximately the same distance fromthe indentations 35 as a cathode having a cylindrical form, or suchindentations may come somewhat nearer the filament if desired, whereuponthe ridges 34sare hea ted by radiation from the filament and also byconduction from the nearer inner portions Such a construction provides auniform heating effect as though a heater were used having a diametersuch that the cylinder walls would come somewhere between the ridges 8eand the indentations 35, this imaginary heater being the mean depthofthe corrugations and the electronemitting. quality of the cathodemaybe greatly increased without the necessity of increasing the currentflowing through the heater. a

It has been found that with the use of a cylindrical cathode certaintorsional strains are setup when the cathode is raised to a hightemperature during the process of exhaustion. These torsional strainsmay distort the cathode slightly so that oneend, generally the upper, iscaused to move slightly out of alignment" with the result that ittouches the filament, which completely destroys the usefulness of thetube, and necessitates scrapping the same. In the present invention thecorrugated cathode provides great strength in the cathode walls whichabsolutely resist any tendency toward distortion when heated and,therefore, the danger of a failure of the tube due to movement of thecathode against the filament or grid is eliminated.

-While I have shown and described a corrugated cathode havinglongitudinal ridges and indentations, it is to be understood that anycross section or formation of the walls which will increase the surfaceof the cathode and at the same time permit the average mass to berelatively close to the heater is within the spirit ofthe invention andit is my intention that the word corrugated as used throughout thespecification and claims, shall coverany such construction;

I have also shown' and described the invention as adapted to be usedwitha rectifying tube but it is obvious that such a cathode may be usedin anyradio vacuum tube such as a detector or amplifier and therefore, I

do not desire to limitmyself'to the specific construction shown anddescribed, butto interpret, the invention broadly, within the scope ofthe appended claims.

What I claim is: i

1'. In a thermionic tube, a-heating filament, a corrugated cathodeadjacent said filament, the corrugations on said cathode extendinglongitudinally thereof, and a strip of metal around each end of saidcathode engaging only the peaks of the corrugations, said strip beingwelded to a plurality of said corrugations.

2.. A cathode for thermionic tubes comprising an elongated shell havinglongitudinal v corrugations around the entire surface thereof providingalternate-depressions and ridges thereby bot-h materially increasing thesurface area and rigidity of said shell throughout its circumference.

3; A cathode for thermionic tubes comprising an elongated shell having acentral axis and-having longitudinal corrugations, the mean depthwhereof by which the heating effect is rated, centers onsaid axis, andthe electron emissive surface is increased materially. v i

4;. A cathode for thermionic'tubes comprising an elongated shell havingalternate longitudinal depressions and ridges of substantial depth andheight respectively as compared to the distance between the peaks .ofsucessive ridges, whereby the rigidity and surfacc'area of the shell arematerially increased,

5. A cathode for thermionic tubes comprising an elongated shell havingcorrugations providing alternate longitudinal depressions and. ridges ofsubstantial depth and height respectively as compared to the distancebetween the peaks of successive ridges, the several peaks and ridgesbeing inversely shaped to each other for obtaining a mean depth ofcorrugations substantially equi-distant from a central axis.

In testimony whereof I aflix my signature.

DANIEL J. DELANEY.

